With continuous evolution of wireless cellular networks, orthogonal multiple access technologies, such as a Code Division Multiple Access (Code Division Multiple Access, “CDMA” for short) technology and an Orthogonal Frequency Division Multiple Access (Orthogonal Frequency Multiple Access, “OFDMA” for short) technology, that are widely applied to a 3rd-generation (3rd-Generation, “3G” for short) mobile communications system and a 4th-generation (4th-Generation, “3G” for short) mobile communications system gradually cannot satisfy people's growing requirements on capacities of cellular networks such as massive access and continuous improvement of spectrum efficiency. In addition, research and application of non-orthogonal multiple access technologies gradually attract more attention from the field and the academic circle. It is expected that a capacity improvement problem can be effectively resolved on future wireless cellular networks such as a 5th-generation (5th-Generation, “5G” for short) mobile communications system by means of the non-orthogonal multiple access technologies.
A sparse code multiple access (Sparse Code Multiple Access, “SCMA” for short) technology is a typical non-orthogonal multiple access and transmission technology. Certainly, the SCMA technology may be referred to as other names in the communications field. According to this technology, M (M is an integer not less than 1) data streams of one or more terminals are overlaid to N (N is an integer not less than 1) subcarriers for sending. Each piece of data of each data stream is extended to the N subcarriers by means of sparse spread spectrum. When a value of M is greater than that of N, this type of technology can effectively improve a network capacity, including a quantity of terminals that can access a system and spectrum efficiency. Therefore, as an important non-orthogonal access technology, the SCMA technology has attracted more attention and become an important candidate access technology in evolution of future wireless cellular networks.
Grant free (Grant free) is a special scheduling mechanism for transmission of small data packets in the SCMA technology, so as to reduce overheads and redundancy resulting from frequent scheduling requests. For an uplink channel, a grant-free terminal no longer requests for a resource, but directly performs uplink transmission on a grant-free resource by using a codebook in at least one codebook and a pilot corresponding to the codebook. A base station performs blind detection on the grant-free resource by using the at least one codebook and the pilot corresponding to the codebook.
For the uplink, the grant-free scheduling manner can reduce uplink resource request signaling, thereby reducing data transmission delays and saving bandwidth.
However, there is no existing technology that relates to how to improve a network capacity, that is, a spectrum multiplex rate, in the transmission mechanism.